Distal [FeS]-Cluster Coordination in [NiFe]-Hydrogenase Facilitates Intermolecular Electron Transfer

Area of Science:

• Biochemistry
• Bioenergetics
• Enzyme catalysis

Background:

• Biohydrogen is a renewable energy source.
• Hydrogenases are enzymes crucial for hydrogen oxidation in enzymatic fuel cells.
• Electron transfer (ET) rates are key to fuel cell efficiency.

Purpose of the Study:

• To investigate the factors influencing electron transfer rates in [NiFe]-hydrogenase.
• To understand the role of the enzyme's iron-sulfur cluster coordination in electron transfer.
• To explore protein engineering strategies for optimizing hydrogenase function.

Main Methods:

• Density Functional Theory (DFT) calculations were used to determine Marcus equation parameters.
• Analysis of the electronic coupling and reorganization energy for different iron-sulfur cluster environments.
• Comparison of wild-type and engineered all-cysteine mutant hydrogenases.

Main Results:

• The electron transfer rate at the electrode surface follows the Marcus equation.
• The coordination sphere of the distal iron-sulfur cluster ([Fe₄S₄](His)(Cys)₃) significantly impacts electron transfer.
• A histidine-to-cysteine substitution minimally affects reorganization energy but diminishes electronic coupling.
• The wild-type enzyme exhibits faster electron transfer due to a fine-tuned protein environment.

Conclusions:

• Protein engineering can modulate electron transfer rates by altering the enzyme's active site.
• Optimizing the electronic coupling and protein environment is crucial for efficient biohydrogen fuel cells.
• This research provides a foundation for designing improved hydrogenase enzymes for energy applications.